1. Field of the Invention
The present invention relates to a galvanometer mirror to be used in optical devices such as information recording/regenerating devices for recording and/or regenerating information on optical media such as magneto-optical disk drives, recordable disk drives, phase transition type disk drives, CD-ROMs, DVDs and optical cards and other optical devices such as optical scanners and optical deflectors for optical communications.
2. Description of the Related Art
In these optical devices, any device for supporting an optical element such as a mirror for bending the path of a light beam has been used. As such a device, for example, Japanese Patent Application Laying-open No. 5-12686 (1993) (hereinafter, simply referred to as JPA 5-12686) discloses a galvanometer mirror to be arranged on a movable part of an optical device as shown in FIG. 1.
The galvanometer mirror shown in FIG. 1 comprises a circular reflective mirror 1, a plurality of driving coils (e.g., five driving coils) 2 wound in a generally square shape on the back surface of the reflective mirror 1 such that each of the square-shaped driving coils 2 may be symmetrical about the center of the reflective mirror 1 and the opposite shorter sides of the driving coil 2 are bent and fixed on the side surfaces of the reflective mirror 1.
The reflective mirror 1 is fixed on the top surface of a mirror-supporting part 3 mounted on a tubular housing 6 through a combination of a hinge 4 and a base 5. As shown in the FIG. 1, the hinge 4 and the base 5 are combined as an integral part concentrically formed on the back surface of the mirror-supporting part 3.
In the housing 6, there is provided a ring-shaped back yoke 7 facing to the side surface of the reflective mirror 1. In addition, there is a multi-polar magnet 8 provided on the inner peripheral surface of the back yoke 7. In this case, magnetic poles of the magnet 8 correspond to the bent portions of the driving coils 3 in a one-to-one relationship. Among the driving coils 2, a current is fed through the desired one to generate oppositely directed forces F1, F2 on the opposite sides thereof such that the refractive mirror 1 can be supported to be driven in multiple directions.
In the galvanometer mirror disclosed in the above reference (JPA 5-12686), for driving in different directions (e.g., five directions), the driving coils 2 are arranged on the movable part such that the number of the driving coils 2 matches the number of directions along which the galvanometer can be driven. In other words, for example, there are five driving coils 2 if the number of directions is five. For feeding currents to these driving coils respectively, therefore, there is a need to provide power-supply lines at least twice as much as the number of the directions (e.g., ten lines for five directions) extending from the fixed portion of the optical device to the reflective mirror 1.
However, JPA 5-12686 does not disclose or teach the power supply to the driving coils 2. If a plurality of lead wires (e.g., ten lead wires) is provided as the power-supply lines, the solidity of the lead wire may be substantially affected on the operation of the reflective mirror 1. Moreover, the form of each lead wire itself is unstable, so that the reflective mirror 1 may be inclined or the operation of the reflective mirror 1 may be varied depending on the direction. Consequently, it may become impossible to drive the reflective mirror 1 in a stable manner.
Therefore, an object of the present invention is to provide a galvanometer mirror which is able to feed a current to a plurality of driving coils easily without substantially affecting the drive of an optical element such as a reflective mirror.
There is provided a galvanometer mirror comprising: a movable part having an optical element and a plurality of coils; a supporting part for supporting the movable part so that the movable part can be inclined toward a predetermined plane around an axis; and a magnetic circuit for applying a magnetic field to the coils, wherein the supporting part has an elastic part that inclines the movable part around the axis by torque around the axis caused by the magnetic field and supplies electric power to the coils.
According to the present invention, the elastic part of the supporting part, such as a spring, is responsible to supply electric power to the coils, so that the need for any lead wire to be used in the power supply to the plurality of the coils can be avoided. Consequently, the power supply can be easily performed without substantially affecting the drive of the optical element such as a reflective mirror.
Preferably, the supporting part may extend in the direction along the axis, so that the optical element can be effectively driven around the axis.
Preferably, the supporting part may comprise a first portion extending in the direction along the axis and a second portion extending in the direction along another axis perpendicular to the axis. Therefore, the optical element can be not only effectively driven around the axis but also effectively driven around another axis.
Preferably, the movable part may be supported so as to be inclined toward the axis and also inclined toward another axis perpendicular to the axis. In this case, for example, the elastic part may include four springs. Each of these springs has a first end portion that extends along the axis and is fixed on the movable part and a second end portion that extends along another axis and is fixed on the movable part, and a coupling part for coupling the first end portion and the second end portion. Alternatively, the elastic part may have at least four independent springs.